The present invention relates to a method and an apparatus for the sterilization of plastics material pre-forms. It is generally known in the field of the drinks production industry that plastics material pre-forms are first made available, and they are then heated in a furnace and are expanded to form plastics material containers by means of blow moulding machines for example.
In this case, in numerous applications or beverages to be filled respectively it is advantageous or necessary for the containers themselves to be sterilized. In particular, the durability of sensitive filling products, in particular in PET bottles, can be decisively improved if the number of germs in the containers is significantly reduced before the filling process. To this end, different wet and dry aseptic methods are known in the field of filling technology. A fundamental drawback with these methods lies in the fact that on account of the large volumes of the containers they require a high consumption of sterilization medium (such as for example peracetic acid or hydrogen peroxide). More recent machine concepts are therefore based upon the fact that the number of the germs is already reduced before the blow moulding of the containers in a blow moulding machine. In other words, the plastics material pre-forms or “pre-forms” (English term) respectively are sterilized in this case. For this purpose the plastics material pre-form passes through a treatment region in which the disinfection is achieved, in particular, by gaseous or liquid sterilization agents or even by irradiation (for example with UV or electron radiation).
If a gaseous sterilization agent such as for example H2O2 is used for the disinfection, then this aggregate state has to be maintained in the treatment region during the entire disinfection process. Only in this way a constantly high concentration of the sterilization medium and, as a result, a robust disinfection process with a constantly high disinfection rate can be ensured.
In particular, however, the housing wall of a treatment room also constitutes a problem with this type of sterilization. In order that the concentration of the sterilization agent should remain constant, it should namely be ensured that the temperature does not drop below the dew point of the mixture at any point.
In the prior art it is customary for this tempering of the wall also to be achieved directly by the sterilization medium or the temperature thereof respectively. This means that the process gas supplied to the sterilizer is set so high that a corresponding tempering of the treatment region or even the walls respectively can be achieved. This leads, however, to an unnecessarily high energy consumption and to a high thermal loading of the mechanical components.
The object of the present invention is therefore to reduce the energy consumption of apparatus of this type. In addition, an excessively high stressing of the individual components of apparatus of this type should preferably also be avoided.